Standard trusses for a mobile home space a roof from inner ceiling panels sufficiently to allow installation of batts of glass fiber insulation between trusses. Conveniently, batts with a nominal thickness of two inches and an insulation value of R7 can be used. Less conveniently, and with some compression of the batts at opposite ends, batts with a nominal thickness of three and one-half inches and an insulation value of R11 can be used.
With the relatively low amount of thermal insulation in such constructions, the significance of the vertical heat flow path through the trusses themselves was not readily apparent. However, with recent emphasis on energy conservation, trusses have been made taller to provide more space between ceiling panels and the roof and thus allow more insulation to be installed, such as a nominal total thickness of eight to nine and one-half inches and an insulatiotn value of R25 to R30. With this relatively high amount of thermal insulation between trusses, the vertical heat flow path through the trusses results at these locales in a more significant, higher percentage of the total heat loss through the roof. The separation of the batts of insulation at the vertical posts or braces of the truss is particularly harmful to heat conservation.